Chapter 1 – Pathology and Classification
WHO classification of bone sarcomas (1)
Primary tumours of bone are relatively rare and bone sarcomas account for only 0.2% of all neoplasms. ~58 different bone tumours are recognised by the WHO.
Most bone tumours show a specific anatomical bone distribution and affect specific age groups.
Approximately 43% of bone sarcomas arise around the knee. The second most common site is the pelvis.
A multidisciplinary approach with correlation between radiological features and morphology is mandatory for correct diagnosis, since the morphology of different tumours (benign and malignant) may show considerable overlap.
Bone tumours vary widely in their biological behavior and are grouped in concordance with STSs into benign, intermediate (locally aggressive/rarely metastasising) or malignant.
In contrast to the FNCLCC STS grading, the histotype determines the histological grade of most bone sarcomas.
Exceptions are chondrosarcoma and leiomyosarcoma, for which separate grading systems are used.
The significance of histological grading in chondrosarcoma is limited by interobserver variability.
REVISION QUESTIONS
1. Is chondrosarcoma typically located in the metaphysis or epiphysis of the long bone?
2. What is mandatory for a correct diagnosis in bone tumours?
3. What is bone sarcoma grading based on?
Classification of STS: histological grading WHO classification of bone sarcomas - 2
